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asam-ev / OpenMATERIAL

3D model exchange format with physical material properties for virtual development, test and validation of automated driving.
Mozilla Public License 2.0
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Add retroreflective material #5

Open LudwigFriedmann opened 2 months ago

LudwigFriedmann commented 2 months ago

Original author: @ClemensLinnhoff

Especially for lidar, retroreflective materials such as road signs and license plates are important.

I suggest either to include a flag if a material is retroreflective for a certain wavelength(region). Or to be more precise, we need to introduce a "retroreflectivity" value, because no material is perfectly retroreflective. If it was, road signs would be dark for the human eye. So there is always a diffuse portion. The problem is, I don't have a good idea how to physically set this parameter.

LudwigFriedmann commented 2 months ago

Specular reflection could potentially be replaced by retro reflection using a binary flag (if true, light is directly reflected to the emitter). What seems to be more complex is diffuse reflection. How could this be modelled in the case of a retro-reflector?

It seems to be unrealistic to model this effect by geometry for camera or LIDAR. For larger wavelengths (e.g. radar), the problem may be solved by geometry...

LudwigFriedmann commented 2 months ago

Original author: @ClemensLinnhoff

Some insights: Retroreflectivity can apparently be quantified by

(Source: http://www.egroupnet.com/3M/tss/minimumreflectivity/retroreflective.asp)

In Germany there are norms classifying traffic signs according to their coefficient of retroreflectivity in three classes: RA1 - RA3. Depending on the class, they can be used e.g. in parking lots, inner city or on the highway (highest class). (Source: https://www.reflexfolie.de/glossar/reflexionsklassen-und-reflexfolienaufbau)

Values of the coefficient of retroreflectivity can also be found for license plates, e.g. here.

There is also measuring equipment for measure the coefficient of retroreflectivity. So at a first glance this seems to be more widely used than the retroreflective efficiency.